Methods and apparatuses for configuring radio terminal with numerology of second RAT via first RAT

ABSTRACT

A second RAN node (2) associated with a second RAT sends a radio resource configuration of the second RAT to a radio terminal (3) via a first RAN node (1) associated with a first RAT. The radio resource configuration explicitly or implicitly indicates at least one numerology that is included in multiple numerologies supported by the second RAT and is different from a reference numerology. It is thus, for example, possible to allow a radio terminal to be configured with a numerology of a cell served by a secondary gNB or a target gNB in Inter-RAT Dual Connectivity between E-UTRA and NR and in a handover from E-UTRA to NR.

TECHNICAL FIELD

The present disclosure relates to a radio communication system and, inparticular, to communication in which a radio terminal simultaneouslyuses multiple cells of different Radio Access Technologies (RATs)operated by different radio stations.

BACKGROUND ART

The 3rd Generation Partnership Project (3GPP) has started in 2016 thestandardization for the fifth generation mobile communication system(5G), i.e., 3GPP Release 14, to make it a commercial reality in 2020 orlater. 5G is expected to be realized by continuous enhancement/evolutionof LTE and LTE-Advanced and an innovative enhancement/evolution by anintroduction of a new 5G air interface (i.e., a new Radio AccessTechnology (RAT)). The new RAT supports, for example, frequency bandshigher than the frequency bands (e.g., 6 GHz or lower) supported byLTE/LTE-Advanced and its continuous evolution. For example, the new RATsupports centimeter-wave bands (10 GHz or higher) and millimeter-wavebands (30 GHz or higher).

In this specification, the fifth generation mobile communication systemis referred to as a 5G System or a Next Generation (NextGen) System (NGSystem). The new RAT for the 5G System is referred to as a New Radio(NR), a 5G RAT, or a NG RAT. A new Radio Access Network (RAN) for the 5GSystem is referred to as a 5G-RAN or a NextGen RAN (NG RAN). A new basestation in the NG-RAN is referred to as a NR NodeB (NR NB) or a gNodeB(gNB). A new core network for the 5G System is referred to as a 5G CoreNetwork (5G-CN) or a NextGen Core (NG Core). A radio terminal (i.e.,User Equipment (UE)) capable of being connected to the 5G System isreferred to as 5G UE or NextGen UE (NG UE), or simply referred to as UE.The official names of the RAT, UE, radio access network, core network,network entities (nodes), protocol layers and the like for the NG Systemwill be determined in the future as standardization work progresses.

The term “LTE” used in this specification includes enhancement/evolutionof LTE and LTE-Advanced to provide interworking with the 5G System,unless otherwise specified. The enhancement/evolution of LTE andLTE-Advanced for the interworking with the 5G System is referred to asLTE-Advanced Pro, LTE+, or enhanced LTE (eLTE). Further, terms relatedto LTE networks and logical entities used in this specification, such as“Evolved Packet Core (EPC)”, “Mobility Management Entity (MME)”,“Serving Gateway (S-GW)”, and “Packet Data Network (PDN) Gateway(P-GW))”, include their enhancement/evolution to provide interworkingwith the 5G System, unless otherwise specified. Enhanced EPC, enhancedMME, enhanced S-GW, and enhanced P-GW are referred to, for example, asenhanced EPC (eEPC), enhanced MME (eMME), enhanced S-GW (eS-GW), andenhanced P-GW (eP-GW), respectively.

In LTE and LTE-Advanced, for achieving Quality of Service (QoS) andpacket routing, a bearer per QoS class and per PDN connection is used inboth a RAN (i.e., an Evolved Universal Terrestrial RAN (E-UTRAN)) and acore network (i.e., EPC). That is, in the Bearer-based QoS (orper-bearer QoS) concept, one or more Evolved Packet System (EPS) bearersare configured between a UE and a P-GW in an EPC, and multiple ServiceData Flows (SDFs) having the same QoS class are transferred through oneEPS bearer satisfying this QoS. An SDF is one or more packet flows thatmatch an SDF template (i.e., packet filters) based on a Policy andCharging Control (PCC) rule. In order to achieve packet routing, eachpacket to be transferred through an EPS bearer contains information foridentifying which bearer (i.e., General Packet Radio Service (GPRS)Tunneling Protocol (GTP) tunnel) the packet is associated with.

In contrast, with regard to the 5G System, it is discussed that althoughradio bearers may be used in the 5G-RAN, no bearers are used in the5G-CN or in the interface between the 5G-CN and the NG-RAN (seeNon-Patent Literature 1). Specifically, PDU flows are defined instead ofan EPS bearer, and one or more SDFs are mapped to one or more PDU flows.A PDU flow between a 5G UE and a user-plane terminating entity in an NGCore (i.e., an entity corresponding to a P-GW in the EPC) corresponds toan EPS bearer in the EPS Bearer-based QoS concept. The PDU flowcorresponds to the finest granularity of the packet forwarding andtreatment in the 5G system. That is, the 5G System adopts the Flow-basedQoS (or per-flow QoS) concept instead of the Bearer-based QoS concept.In the Flow-based QoS concept, QoS is handled per PDU flow. In the QoSframework of the 5G system, a PDU flow is identified by a PDU flow IDcontained in a header encapsulating a Service Data Unit of a tunnel of aNG3 interface. The NG3 interface is a user plane interface between the5G-CN and the gNB (i.e., 5G-RAN). Association between a 5G UE and a datanetwork is referred to as a “PDU session”. The term “PDU session”corresponds to the term “PDN connection” in LTE and LTE-Advanced.Multiple PDU flows can be configured in one PDU session.

The PDU flow is also referred to as a “QoS flow”. The QoS flow is thefinest granularity in QoS treatment in the 5G system. User plane traffichaving the same NG3 marking value in a PDU session corresponds to a QoSflow. The NG3 marking corresponds to the above-described PDU flow ID,and it is also referred to as a QoS flow ID or a Flow IdentificationIndicator (FII).

It has also been suggested that the 5G System supports network slicing(see Non Patent Literature 1). Network slicing uses Network FunctionVirtualization (NFV) and software-defined networking (SDN) techniquesand makes it possible to generate multiple virtualized logical networkson a physical network. Each virtualized logical network is referred toas a network slice or a network slice instance, includes logical nodesand functions, and is used for specific traffic and signaling. The5G-RAN or the 5G-CN or both have a Slice Selection Function (SSF). TheSSF selects one or more network slices suitable for a 5G UE based oninformation provided by at least one of the 5G UE and the 5G-CN.

FIG. 1 shows a basic architecture of the 5G system. A UE establishes oneor more Signalling Radio Bearers (SRBs) and one or more Data RadioBearers (DRBs) with a gNB. The 5G-CN and the gNB establish a controlplane interface and a user plane interface for the UE. The control planeinterface between the 5G-CN and the gNB (i.e., RAN) is referred to as anNG2 interface or an NG-c interface and is used for transfer ofNon-Access Stratum (NAS) information and for transfer of controlinformation (e.g., NG2 AP Information Element) between the 5G-CN and thegNB. The user plane interface between the 5G-CN and the gNB (i.e., RAN)is referred to as an NG3 interface or an NG-u interface and is used fortransfer of packets of one or more PDU flows in a PDU session of the UE.

Note that, the architecture shown in FIG. 1 is merely one of the 5Garchitecture options or deployment scenarios (see Annex J of Non-PatentLiterature 1 and see Non-Patent Literature 2). The architecture shown inFIG. 1 is referred to as “Standalone NR (in NextGen System)” or “Option2”. In contrast, FIGS. 2 and 3 show architecture Options 3 and 3A, whichare referred to as “Non-standalone NR in EPS”. In FIGS. 2 and 3, controlinterfaces are shown as dashed lines, while user plane interfaces areshown as solid lines. Architecture Options 3 and 3A are Dualconnectivity (DC) deployments including E-UTRA as the anchor RAT (or theprimary RAT or the master RAT) and NR as a secondary RAT. In Options 3and 3A, E-UTRA (LTE eNB) and NR (gNB) are connected to the EPC. The NRuser plane connection to the EPC goes through the LTE eNB in Option 3,whereas in Option 3A, it passes directly through a user plane interfacebetween the gNB and the EPC.

Non-Patent Literature 3 has suggested that in Architecture Options 3 and3A, which are DC architecture where E-UTRA and NR are connected to theEPC, the NR gNB supports the LTE DC functionalities and procedures.Non-Patent Literature 3 has also suggested that in the DC architecturewhere E-UTRA and NR are connected to the EPC, the NR gNB applies the LTEQoS framework (i.e., bearer based QoS) to the EPC, the LTE eNB and theUE. Further, Non-Patent Literature 3 has suggested the followingproposals:

LTE DC procedures (e.g., SeNB addition) are applied when adding NR gNBas secondary node, in which necessary QoS service (i.e., bearer) areconfigured;

E-UTRAN Radio Access Bearer (E-RAB) is established between EPC and NRgNB for Secondary Cell Group (SCG) bearer option according to LTE;

X2-U is established between LTE eNB and NR gNB for split bearer optionaccording to LTE; and

DRB is established between NR gNB and UE according to SCG bearer optionor split bearer option according to LTE.

Non-Patent Literature 4 has suggested that there is one-to-one mapping(1:1 mapping) between S1-U and DRB of SCG (i.e., SCG bearer). Non-PatentLiterature 4 has also suggested that QoS attributes of EPC are in usefor EPS bearers and, accordingly, there is a need to map the QoSparameters used in EPC to the radio bearer parameters used in the NR.

In addition, the NR is expected to use different sets of radioparameters in multiple frequency bands. Each radio parameter set isreferred to as “numerology”. OFDM numerology for an Orthogonal FrequencyDivision Multiplexing (OFDM) system includes, for example, subcarrierspacing, system bandwidth, Transmission Time Interval (TTI) length,subframe duration, cyclic prefix length, and symbol duration. The 5Gsystem supports various types of services having different servicerequirements, including, for example, enhanced Mobile Broad Band (eMBB),Ultra Reliable and Low Latency Communication (URLLC), and M2Mcommunication with a large number of connections (e.g., massive MachineType Communication (mMTC)). Numerology selection depends on servicerequirements.

The UE and the NR gNB in the 5G system support aggregation of multipleNR carriers with different numerologies. The 3GPP discusses achievementof aggregation of multiple NR carriers with different numerologies bylower layer aggregation, such as the existing LTE Carrier Aggregation(CA), or higher layer aggregation, such as the existing DualConnectivity (see, for example, Non-Patent Literature 5 to 7).

CITATION LIST Non Patent Literature

-   [Non-Patent Literature 1] 3GPP TR 23.799 V14.0.0 (2016-12) “3rd    Generation Partnership Project; Technical Specification Group    Services and System Aspects; Study on Architecture for Next    Generation System (Release 14)”, December 2016-   [Non-Patent Literature 2] 3GPP TR 38.801 V1.0.0 (2016-12) “3rd    Generation Partnership Project; Technical Specification Group Radio    Access Network; Study on New Radio Access Technology; Radio Access    Architecture and Interfaces (Release 14)”, December 2016-   [Non-Patent Literature 3] 3GPP R2-168400, NTT DOCOMO, INC., “QoS and    bearer for DC between LTE and NR”, 3GPP TSG-RAN WG2 Meeting #96,    Reno, USA, 14-18 Nov. 2016-   [Non-Patent Literature 4] 3GPP R2-168686, Nokia, Alcatel-Lucent    Shanghai Bell, “EPC-NR PDCP interaction for tight interworking: User    Plane aspects”, 3GPP TSG-RAN WG2 Meeting #96, Reno, USA, 14-18 Nov.    2016-   [Non-Patent Literature 5] 3GPP TR 38.804 V0.4.0 (2016-11) “3rd    Generation Partnership Project; Technical Specification Group Radio    Access Network; Study on New Radio Access Technology; Radio    Interface Protocol Aspects (Release 14)”, November 2016-   [Non-Patent Literature 6] 3GPP R2-164788, Nokia, Alcatel-Lucent    Shanghai Bell, “Carrier Aggregation between carriers of different    air interface numerologies”, 3GPP TSG-RAN WG2 Meeting #95,    Gothenburg, Sweden, 22-26 Aug. 2016-   [Non-Patent Literature 7] 3GPP R2-165328, “Aggregation of carriers    in NR”, 3GPP TSG-RAN WG2 Meeting #95, Gothenburg, Sweden, 22-26 Aug.    2016

SUMMARY OF INVENTION Technical Problem

The present inventors have studied interworking between E-UTRA and NRand found several problems. For example, the Secondary gNB (SgNB)serving as the secondary node supports multiple numerologies in DCarchitecture in which E-UTRA and NR are connected to the EPC (i.e.,architecture options 3 and 3A). The 5G UE is also able to use multiplenumerologies in one cell or between multiple cells simultaneously (thatis, in one RRC connection). However, it is not clear how to perform aradio resource configuration regarding numerology of the SCG cell (orSCG carrier) on the UE when the SgNB supports multiple numerologies andthe UE uses them.

The above problem regarding Numerology may occur also in other E-UTRA-NRDC architecture options (e.g., architecture options 7 and 7A). Thearchitecture options 7 and 7A are Dual connectivity (DC) deploymentsincluding E-UTRA serving as the anchor RAT (or the primary RAT or themaster RAT) and NR serving as the secondary RAT. In the options 7 and7A, E-UTRA (LTE eNB) and NR (gNB) are connected to the 5G-CN. The NRuser plane connection to the 5G-CN goes through the LTE eNB in theoption 7, whereas in the option 7A, it directly passes through the userplane interface between the gNB and the 5G-CN. In the options 7 and 7Aas well, it is also not clear how to perform a radio resourceconfiguration regarding numerology of the SCG cell (or SCG carrier) onthe UE when the SgNB supports multiple numerologies and the UE usesthem.

A similar problem regarding Numerology may occur also in an Inter-RAThandover from E-UTRA to NR. That is, it is not clear how to perform aradio resource configuration regarding numerology of the target NR cellon the UE when the UE is handed over from the source LTE eNB to thetarget gNB that supports multiple numerologies.

Accordingly, one of the objects to be attained by embodiments disclosedherein is to provide an apparatus, a method, and a program that allow aUE to be configured with a numerology of a cell served by a secondarygNB or a target gNB in Inter-RAT Dual Connectivity between E-UTRA and NRand in an Inter-RAT handover from E-UTRA to NR. It should be noted thatthis object is merely one of the objects to be attained by theembodiments disclosed herein. Other objects or problems and novelfeatures will be made apparent from the following description and theaccompanying drawings.

Solution to Problem

In a first aspect, a second radio access network (RAN) node is used in aradio communication system. The radio communication system supports afirst RAT and a second RAT. The second RAN node includes a memory and atleast one processor coupled to the memory. The at least one processor isconfigured to send a radio resource configuration of the second RAT to aradio terminal via a first RAN node associated with the first RAT. Theradio resource configuration explicitly or implicitly indicates at leastone numerology that is included in multiple numerologies supported bythe second RAT and is different from a reference numerology

In a second aspect, a first radio access network (RAN) node is used in aradio communication system. The radio communication system supports afirst RAT and a second RAT. The first RAN node includes a memory and atleast one processor coupled to the memory. The at least one processor isconfigured to receive a radio resource configuration of the second RATfrom a second RAN node associated with the second RAT and send the radioresource configuration to a radio terminal. The radio resourceconfiguration explicitly or implicitly indicates at least one numerologythat is included in multiple numerologies supported by the second RATand is different from a reference numerology.

In a third aspect, a radio terminal is used in a radio communicationsystem. The radio communication system supports a first RAT and a secondRAT. The radio terminal includes at least one wireless transceiver andat least one processor. The at least one wireless transceiver isconfigured to communicate with a first radio access network (RAN) nodeassociated with the first RAT and communicate with a second RAN nodeassociated with the second RAT. The at least one processor is configuredto receive a radio resource configuration of the second RAT from thesecond RAN node via the first RAN node. The radio resource configurationexplicitly or implicitly indicates at least one numerology that isincluded in multiple numerologies supported by the second RAT and isdifferent from a reference numerology.

In a fourth aspect, a method for a second radio access network (RAN)node includes sending a radio resource configuration of the second RATto a radio terminal via a first RAN node associated with the first RAT.The radio resource configuration explicitly or implicitly indicates atleast one numerology that is included in multiple numerologies supportedby the second RAT and is different from a reference numerology.

In a fifth aspect, a method for a first radio access network (RAN) nodeincludes receiving a radio resource configuration of the second RAT froma second RAN node associated with the second RAT, and sending the radioresource configuration to a radio terminal. The radio resourceconfiguration explicitly or implicitly indicates at least one numerologythat is included in multiple numerologies supported by the second RATand is different from a reference numerology.

In a sixth aspect, a method for a radio terminal includes receiving aradio resource configuration of the second RAT from a second radioaccess network (RAN) node associated with the second RAT via a first RANnode associated with the first RAT. The radio resource configurationexplicitly or implicitly indicates at least one numerology that isincluded in multiple numerologies supported by the second RAT and isdifferent from a reference numerology.

In a seventh aspect, a program includes instructions (software codes)that, when loaded into a computer, cause the computer to perform themethod according to the above-described fourth, fifth, or sixth aspect.

Advantageous Effects of Invention

According to the above-deceived aspects, it is possible to provide anapparatus, a method, and a program that allow a UE to be configured witha numerology of a cell served by a secondary gNB or a target gNB inInter-RAT Dual Connectivity between E-UTRA and NR and in an Inter-RAThandover from E-UTRA to NR.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing basic architecture of the 5G Systemaccording to the Background Art;

FIG. 2 is a diagram showing Architecture Option 3 for Dual Connectivitywhere E-UTRA (LTE eNB) and NR (gNB) are connected to EPC, according tothe Background Art;

FIG. 3 is a diagram showing Architecture Option 3A for Dual Connectivitywhere E-UTRA (LTE eNB) and NR (gNB) are connected to EPC, according tothe Background Art;

FIG. 4 is a diagram showing a configuration example of a radiocommunication network according to a plurality of embodiments;

FIG. 5 is a sequence diagram showing an example of an SCG establishmentprocedure according to a first embodiment;

FIG. 6 is a sequence diagram showing an example of signaling between anMeNB and an SgNB according to a second embodiment;

FIG. 7 is a flowchart showing an example of an operation of an LTE eNB(MeNB) according to the second embodiment;

FIG. 8 is a flowchart showing an example of an operation of a NR gNB(SgNB) according to a third embodiment;

FIG. 9 is a diagram showing a configuration example of a radiocommunication network according to a fourth embodiment;

FIG. 10 is a sequence diagram showing an example a procedure of anInter-RAT handover according to the fourth embodiment;

FIG. 11 is a block diagram showing a configuration example of a NR gNBaccording to a plurality of embodiments; and

FIG. 12 is a block diagram showing a configuration example of a UEaccording to a plurality of embodiments.

DESCRIPTION OF EMBODIMENTS

Specific embodiments will be described hereinafter in detail withreference to the drawings. The same or corresponding elements aredenoted by the same symbols throughout the drawings, and duplicatedexplanations are omitted as necessary for the sake of clarity.

Each of the embodiments described below may be used individually, or twoor more of the embodiments may be appropriately combined with oneanother. These embodiments include novel features different from eachother. Accordingly, these embodiments contribute to attaining objects orsolving problems different from one another and contribute to obtainingadvantages different from one another.

The following descriptions on the embodiments mainly focus on DCarchitecture where E-UTRA and NR are connected to EPC. However, theseembodiments may be applied to other radio communication systemssupporting DC architecture where different RATs using different QoSframeworks are connected to a common core network.

First Embodiment

FIG. 4 shows a configuration example of a radio communication networkaccording to a plurality of embodiments including this embodiment. Inthe example shown in FIG. 4, the radio communication network includes anLTE eNB 1, an NR gNB 2, a UE 3, and an EPC 4. The radio communicationnetwork shown in FIG. 4 supports dual connectivity (DC) and alsosupports one or both of the above-described option 3 and option 3A. Theoptions 3 and 3A support dual connectivity involving E-UTRA and NR,which are an anchor RAT (or a primary RAT) and a secondary RAT,respectively. In the options 3 and 3A, both E-UTRA (i.e., the LTE eNB 1)and NR (i.e., the gNB 2) are connected to the EPC 4. In the option 3,the NR user plane connection to the EPC 4 goes through the LTE eNB 1,and accordingly user packets of the UE 3 are transferred via aninter-base station interface 403 and via an interface 401 between theeNB 1 and the EPC. In contrast, in the option 3A, the NR user planeconnection to the EPC 4 directly passes through a user plane interface404 between the gNB 2 and the EPC 4.

The UE 3 has a capability to simultaneously communicate with the eNB 1associated with the primary RAT (E-UTRA) and the gNB 2 associated withthe secondary RAT (NR). In other words, the UE 3 has a capability toaggregate a cell of the eNB 1 associated with the primary RAT (E-UTRA)with a cell of the gNB 2 associated with the secondary RAT (NR).Further, in other words, the UE 3 has a capability to be configured withboth a cell of the eNB 1 associated with the primary RAT (E-UTRA) and acell of the gNB 2 associated with the secondary RAT (NR). In thearchitecture options 3 and 3A, an air interface 402 between the eNB 1and the UE 3 provides a control plane connection and a user planeconnection. Meanwhile, an air interface 405 between the gNB 2 and the UE3 includes at least a user plane connection, but it does not need toinclude a control plane connection. In the DC architecture in whichE-UTRA and NR are connected to the EPC 4, the master eNB (MeNB) 1provides one or more E-UTRA MCG cells for the UE 3, while the secondarygNB (SgNB) 2 provides one or more NR SCG cells for the UE 3.

The EPC 4 includes multiple core network nodes including an MME 5 and anS-GW 6. The MME 5 is a control plane node while the S-GW 6 is a userplane node. The MME 5 performs mobility management and bearer managementof UEs that have already attached to the core network (i.e., UEs inEMM-REGISTERED state). The mobility management is used to keep track ofthe current position of each UE and includes maintaining a mobilitymanagement context (MM context) regarding each UE. The bearer managementincludes controlling establishment of an EPS bearer for enabling each UEto communicate with an external network (Packet Data Network (PDN))through E-UTRAN including the eNB 1 and through the EPC 4, andmaintaining an EPS bearer context regarding each UE. The S-GW 6 is agateway with E-UTRAN and is connected via an S1-U interface to one orboth of the eNB 1 and the gNB 2.

The gNB 2 supports multiple numerologies in one or more NR carriers (orcells). That is, one or more numerologies are associated with one NRcell. Numerology includes at least one of subcarrier spacing, systembandwidth, a Transmission Time Interval (TTI) length, subframe duration,slot duration, the number of slots per subframe, a Cyclic prefix length,symbol duration, and the number of symbols per subframe. When the systembandwidth corresponds to the bandwidth supported by aggregation ofmultiple carriers (i.e. Carrier Aggregation (CA)) in UE viewpoints, thenumerology may further include information regarding the correspondencebetween the bandwidth of the multiple aggregated carriers and the systembandwidth. The multiple numerologies include at least one referencenumerology and at least one dedicated or additional numerology that isdifferent from the reference numerology. The reference numerologydefines a reference subframe configuration for the NR carrier(s) thatthe gNB 2 supports (e.g., reference subframe duration, the referencenumber of OFDM symbols per subframe, or a reference TTI length). Theinformation regarding the reference numerology may be transmitted insystem information (e.g., Master Information Block), or may be definedin the standard specification so that it is uniquely determined withrespect to a carrier frequency, or may be detected by the UE 3 byreceiving a synchronisation signal (e.g., a Primary SynchronisationSignal (PSS) or a Secondary Synchronisation Signal (SSS)).

The following describes a procedure for configuring the UE 3 with anumerology(ies) of an SCG cell(s) served by the secondary gNB (SgNB) 2in DC architecture in which E-UTRA and NR are connected to the EPC 4.The gNB 2 according to this embodiment is configured to send an NR radioresource configuration for E-UTRA-NR Dual Connectivity (DC) to the UE 3via the master eNB (MeNB) 1. The NR radio resource configurationexplicitly or implicitly indicates at least one dedicated numerologythat is included in multiple numerologies supported by one or more NRcells within the SCG of the SgNB 2 and is different from the referencenumerology. That is, the NR radio resource configuration includes atleast information regarding the dedicated numerology. The informationregarding the dedicated numerology may include an information elementexplicitly indicating the dedicated numerology, or may include aninformation element indicating a radio parameter(s) that is necessary toderive the dedicated numerology. The dedicated numerology may be, forexample, subcarrier spacing, system bandwidth, a TTI length, subframeduration, slot duration, the number of slots per subframe, a Cyclicprefix length, symbol duration, or the number of symbols per subframe,or any combination thereof. The NR radio resource configuration may bereferred to as an SCG radio configuration or an SCG-Config. The MeNB 1is configured to receive the NR radio resource configuration from theSgNB 2 and send it to the UE 3. The UE 3 is configured to receive the NRradio resource configuration for E-UTRA-NR DC from the SgNB 2 via theMeNB 1.

In some implementations, the SgNB 2 may receive a radio bearer setuprequest from the MeNB 1, and select at least one dedicated numerologyaccording to requirements for an NR Data Radio Bearer (DRB) for the UE 3indicated by the radio bearer setup request. The radio bearer setuprequest is a message for causing the gNB 2 to configure an NR DRB forE-UTRA-NR DC. This radio bearer setup request may be referred to as anSgNB Addition Request. The requirements for an NR DRB may include one orboth of QoS requirements and a service type. The QoS requirementsinclude at least one of: a priority required for an NR DRB, or for anetwork bearer or a flow associated with the NR DRB; a Maximum Bit Rate(MBR); and an Allocation and Retention Priority (ARP). The service typeindicates, for example, one of enhanced Mobile Broad Band (eMBB), UltraReliable and Low Latency Communication (URLLC), and massive Machine TypeCommunication (mMTC).

The SgNB 2 may include in the NR radio resource configuration aninformation element indicating the selected at least one dedicatednumerology. In this case, the SgNB 2 may send the NR radio resourceconfiguration, which explicitly or implicitly indicates the selected atleast one numerology, to the MeNB 1 using a response message (e.g., anSgNB Addition Request Acknowledge message) in response to the radiobearer setup request. The MeNB 1 may transmit the NR radio resourceconfiguration received from the SgNB 2 to the UE 3 using an RRCConnection Reconfiguration message.

FIG. 5 is a sequence diagram showing a process 500 that is one exampleof an SCG establishment procedure according to this embodiment. Theprocedure shown in FIG. 5 basically follows the SeNB Addition procedurein LTE DC. In Step 501, the MeNB 1 sends an SgNB Addition Requestmessage to the SgNB 2. The SgNB Addition Request message requests theSgNB 2 to configure a radio bearer (i.e., SCG DRB) for DC that usesE-UTRA and NR as respectively the primary RAT and the secondary RAT.

The SgNB Addition Request message corresponds to the above-described“radio hearer setup request”. Specifically, the SgNB Addition Requestmessage includes an “SgNB Security Key (for SCG bearer)” informationelement (IE), an “E-RAB To Be Added List” IE, and an “MeNB to SgNBContainer” IE. The “E-RAB To Be Added List” IE includes an E-RAB ID andE-RAB Level QoS Parameters of each E-RAB required by the MeNB 1 to beestablished. The “MeNB to SgNB Container” IE includes an RRC:SCG-ConfigInfo message. The RRC: SCG-ConfigInfo message is used by theMeNB in order to request the SgNB to establish, modify, or release anSCG. The SCG-ConfigInfo message includes, for example, an EPS bearerIdentity, a DRB Identity, and a DRB type. The security policy (e.g.,security algorithm) used in a cell (e.g., radio link, AS layer) of thesecondary RAT (NR) may be different from that used in a cell (e.g.,radio link, Access Stratum (AS) layer) of the primary RAT (E-UTRA). Inthis case, the SgNB Security Key IE may include information regardingthe security policy used in a cell of the secondary RAT (NR). Further,the SgNB 2 may include this security policy-related information into anRRC: SCG-Config message to be transmitted to the UE 3.

In Step 502, the SgNB 2 sends an SgNB Addition Request Acknowledgemessage to the MeNB 1. The SgNB Addition Request Acknowledge message isa response message to the SgNB Addition Request message. The SgNBAddition Request Acknowledge message includes a radio resourceconfiguration for an SCG DRB generated by the SgNB 2. This SCG DRB radioresource configuration is sent to the UE 3 via the MeNB 1. The SCG DRBradio resource configuration indicates at least one dedicated numerologyselected by the SgNB 2.

Specifically, the SgNB Addition Request Acknowledge message includes an“E-RAB Admitted To Be Added List” IE and an “SgNB to MeNB Container” IE.The “SgNB to MeNB Container” IE includes an RRC: SCG-Config message. TheRRC: SCG-Config message is used to transfer a radio resourceconfiguration generated by the SgNB 2. The RRC: SCG-Config messageindicates at least one dedicated numerology selected by the SgNB 2.

In Step 503, the MeNB 1 sends an RRC Connection Reconfiguration messageto the UE 3 in response to receiving the SgNB Addition RequestAcknowledge message from the SgNB 2. This RRC Connection Reconfigurationmessage includes the RRC: SCG-Config message, which has been sent fromthe SgNB 2 to the MeNB 1 via the SgNB Addition Request Acknowledgemessage. The AS layer of the primary RAT (i.e., E-UTRA (LTE)) in the UE3 receives this RRC Connection Reconfiguration message in an E-UTRA cellof the MeNB 1 (i.e., the Primary Cell (PCell)). The AS layer of thesecondary RAT (i.e., NR) in the UE 3 configures, in accordance with theRRC: SCG-Config message, an SCG DRB according to the at least onededicated numerology selected by the SgNB 2.

In Step 504, the UE 3 (i.e., the E-UTRA AS layer) sends an RRCConnection Reconfiguration Complete message to the MeNB 1 in the E-UTRAcell of the MeNB 1 (i.e., PCell). Meanwhile, the UE 3 (i.e., the NR ASlayer) starts a procedure for synchronizing with the SgNB 2 (e.g.,Random Access Procedure).

In Step 505, the MeNB 1 sends an SgNB Reconfiguration Complete messageto the SgNB 2 in response to receiving the RRC ConnectionReconfiguration Complete message from the UE 3.

As can be understood from the above description, the SgNB 2 according tothis embodiment is configured to send the NR radio resourceconfiguration for E-UTRA-NR DC to the UE 3 via the master eNR (MeNB) 1,and the NR radio resource configuration indicates at least one dedicatednumerology that is included in the multiple numerologies supported byone or more NR cells of the SgNB 2 and is different from the referencenumerology. This allows the SgNB 2 to configure the UE 3 with thenumerology(ies) of the SCG cell(s) served by the SgNB 2 in E-UTRA-NR DC.The UE 3 thus can know the numerology(ies) that should be used in theSCG cell(s) served by the SgNB 2.

Second Embodiment

A configuration example of a radio communication network according tothis embodiment is similar to that shown in FIG. 4. This embodimentprovides an improvement that enables the MeNB 1 to use a UE measurementreport indicating a measurement result of an NR cell(s) of the SgNB 2based on a reference numerology(ies) in E-UTRA-NR DC.

The SgNB 2 according to this embodiment is configured to notify the MeNB1 of at least one reference numerology in a setup procedure of aninter-base station interface between the SgNB 2 and the MeNB 1 (e.g., anXn interface or an X3 interface). As already described above, thereference numerology defines the reference subframe duration for the NRcarrier supported by the gNB 2.

FIG. 6 is a sequence diagram showing a process 600 that is one exampleof signaling between the MeNB 1 and the SgNB 2. In Step 601, the SgNB 2notifies the MeNB 1 of multiple numerologies supported in one or more NRcarriers used by the SgNB 2 via an Xn Setup Request message or an XnSetup Response message. The numerologies supported by the SgNB 2 includeat least one reference numerology.

In some implementations, the MeNB 1 may use the referencenumerology(ies) of the SgNB 2 for UE measurement. FIG. 7 is a flowchartshowing a process 700 that is one example of the operation of the MeNB1. In Step 701, the MeNB 1 generates a measurement configurationindicating the reference numerology(ies) of the NR cell(s) served by theSgNB 2. In Step 702, the MeNB 1 sends the generated measurementconfiguration to the UE 3. The measurement configuration causes the UE 3to measure the NR cell(s) of the SgNB 2 based on the referencenumerology(ies) specified in the measurement configuration. Accordingly,the MeNB 1 is able to use a UE measurement report indicating ameasurement result of the NR cell(s) of the SgNB 2 based on thereference numerology(ies). The MeNB 1 may use the measurement result ofthe NR cell(s) of the SgNB 2 based on the reference numerology(ies) inorder to determine start, stop, or modification of E-UTRA-NR DC.

Third Embodiment

A configuration example of a radio communication network according tothis embodiment is similar to that shown in FIG. 4. This embodimentprovides an improvement that enables the SgNB 2 to instruct the UE 3 toperform measurement of an NR cell(s) of the SgNB 2 based on a referencenumerology(ies) in E-UTRA-NR DC.

The SgNB 2 according to this embodiment is configured to send to the UE3, via the MeNB 1, a configuration for measurement on the carrier of theSgNB 2 according to the reference numerology. FIG. 8 is a flowchartshowing a process 800 that is one example of the operation of the SgNB2. In Step 801, the SgNB 2 generates a measurement configurationindicating the reference numerology(ies) of the NR cell(s) served by theSgNB 2. In Step 802, the SgNB 2 sends the generated measurementconfiguration to the UE 3 via the MeNB 1. To be more specific, the MeNB1 may receive the measurement configuration from the SgNB 2 and transmitit to the UE 3. The measurement configuration causes the UE 3 to measurethe NR cell(s) of the SgNB 2 based on the reference numerology(ies)specified in the measurement configuration. Accordingly, the MeNB 1 isable to use a UE measurement report indicating a measurement result ofthe NR cell(s) of the SgNB 2 based on the reference numerology(ies). TheMeNB 1 may use the measurement result of the NR cell(s) of the SgNB 2based on the reference numerology(ies) in order to determine start,stop, or modification of E-UTRA-NR DC.

Fourth Embodiment

This embodiment provides an improvement that allows a UE to beconfigured with a numerology(ies) of a cell(s) served by a secondary gNBor a target gNB in other E-UTRA-NR DC architectures (e.g., thearchitecture options 7 and 7A) and an Inter-RAT handover from E-UTRA toNR.

FIG. 9 shows a configuration example of a radio communication networkaccording to this embodiment. In one example, the radio communicationnetwork according to this embodiment may provide E-UTRA-NR DCarchitecture option 7 or 7A. In the options 7 and 7A, E-UTRA (i.e., theLTE eNB 1) and NR (i.e., the gNB 2) are connected to a 5G-CN 7. In theoption 7, the NR user plane connection to the 5G-CN 7 goes through theLTE eNB 1, and thus user packets of the UE 3 passes through theinter-base station interface 403 and through the interface 901 betweenthe eNB 1 and the 5G-CN 7. In contrast, in the option 7A, the NR userplane connection to the 5G-CN 7 directly passes through the user planeinterface 902 between the gNB 2 and the 5G-CN 7.

The following describes a procedure for configuring the UE 3 with anumerology(ies) of an SCG cell(s) served by the secondary gNB (SgNB) 2in DC architecture in which E-UTRA and NR are connected to the 5G-CN 7.The gNB 2 according to this embodiment may operate in a way similar tothat in the gNB 2 according to the first embodiment. Specifically, inthis embodiment, the gNB 2 is configured to send an NR radio resourceconfiguration for E-UTRA-NR Dual Connectivity (DC) to the UE 3 via themaster eNB (MeNB) 1. The NR radio resource configuration indicates atleast one dedicated numerology that is included in multiple numerologiessupported by one or more NR cells within the SCG of the SgNB 2 and isdifferent from the reference numerology.

The operations of the MeNB 1, the SgNB 2, and the UE 3 may be similar tothose in the SCG establishment procedure (Process 500) described withreference to FIG. 5. Specifically, the SgNB 2 may send an SgNB AdditionRequest Acknowledge message containing an RRC: SCG-Config message thatindicates at least one dedicated numerology selected by the SgNB 2 (Step502). The MeNB 1 may send to the UE 3 an RRC Connection Reconfigurationmessage containing the RRC: SCG-Config message indicating the at leastone dedicated numerology selected by the SgNB 2 (Step 503). The AS layerof the secondary RAT (i.e., NR) in the UE 3 may configure, in accordancewith the RRC: SCG-Config message, an SCG DRB according to the at leastone dedicated numerology selected by the SgNB 2 (Step 504).

Further or alternatively, the radio communication network according tothis embodiment may support an Inter-RAT handover from an E-UTRA cell 11of the LTE eNB 1 to an NR cell 21 of the NR gNB 2. The followingdescribes a procedure for configuring the UE 3 with a numerology(ies) ofthe cell 21 served by the target NR gNB 2 when the UE 3 is handed overfrom the source E-UTRA cell 11 to the target NR cell 21.

FIG. 10 is a sequence diagram showing a process 1000 that is one exampleof an Inter-RAT handover procedure according to this embodiment. In Step1001, the source LTE eNB 1 sends an NR Handover Request message to thetarget gNB 2 on the direct inter-base station interface 403 (e.g., an Xninterface or an X3 interface). The NR Handover Request message in Step1001 may include a Handover Type Information Element (IE) indicating ahandover from LTE to NR. For example, the Handover Type IE is set to“LTEtoNR”.

In Step 1002, the target gNB 2 generates a UE context based on the NRHandover Request message and allocates resources. Then the target gNB 2sends an NR Handover Request Acknowledge message to the source eNB 1.The NR Handover Request Acknowledge message is a response message to theNR Handover Request message. The NR Handover Request Acknowledge messageincludes a radio resource configuration of a DRB of the target NR cell21 generated by the target gNB 2. The radio resource configuration issent to the UE 3 via the source eNB 1. This radio resource configurationindicates at least one dedicated numerology selected by the target gNB2.

To be more specific, the NR Handover Request Acknowledge messagecontains a “Target to Source Transparent Container” IE. The “Target toSource Transparent Container” IE includes radio resource configurationinformation set up by the target gNB 2. This radio resourceconfiguration information indicates at least one dedicated numerologyprovided in the target NR cell 21.

In Step 1003, the source eNB 1 sends to the UE 3 an RRC message thatcontains a Handover Command message including the radio resourceconfiguration information generated by the target gNB 2. This RRCmessage may be, for example, a Mobility from EUTRA command message ormay be an RRC Connection Reconfiguration message. The source eNB 1 mayinclude the radio resource configuration information generated by thetarget gNB 2 into the “MobilityControlInfoNR” IE within the RRCConnection Reconfiguration message.

In Step 1004, the UE 3 moves to a cell of the target RAN (i.e., NR) inresponse to receiving the RRC message that contains the Handover Commandmessage and executes a handover in accordance with the radio resourceconfiguration information provided by the Handover Command message. TheUE 3 thus establishes a radio connection with the target gNB 2 accordingto at least one dedicated numerology selected by the SgNB 2. Theinformation regarding which numerology should be used to execute ahandover (or which numerology should be assumed at the time of theexecution of a handover) may be transmitted in the Handover Commandmessage or the RRC message including this Handover Command message. TheUE 3 executes a handover in accordance with this information (e.g.,establishes the radio connection).

In Step 1005, the UE 3 sends the Handover Confirm for NR message to thetarget gNB 2 after it has successfully synchronized with the target NRcell 21. The message in Step 1005 may be an (NR) RRC ConnectionReconfiguration Complete message.

As can be understood from the above description, in one example, the gNB2 according to this embodiment is configured to send the NR radioresource configuration for E-UTRA-NR DC (i.e., option 7 or 7A) to the UE3 via the MeNB 1, and the NR radio resource configuration indicates atleast one dedicated numerology that is included in the multiplenumerologies supported by one or more NR cells of the SgNB 2 and isdifferent from the reference numerology. This allows the SgNB 2 toconfigure the UE 3 with numerology(ies) of the SCG cell(s) served by theSgNB 2 in E-UTRA-NR DC (i.e., option 7 or 7A). The UE 3 thus can knowthe numerology(ies) that should be used in the SCG cell(s) served by theSgNB 2.

In another example, the gNB 2 according to this embodiment is configuredto send to the UE 3, via the source eNB 1, the NR radio resourceconfiguration for an Inter-RAT handover from E-UTRA to NR, and the NRradio resource configuration indicates at least one dedicated numerologythat is included in the multiple numerologies supported by one or moreNR cells of the target gNB 2 and is different from the referencenumerology. This allows the target gNB 2 to configure the UE 3 with thenumerology(ies) of the target NR cell(s) in the Inter-RAT handover fromE-UTRA to NR. The UE 3 can thus know the numerology(ies) that should beused in at least one NR cell 21 served by the target gNB 2.

The following provides configuration examples of the LTE eNB 1, the NRgNB 2, and the UE 3 according to the above embodiments. FIG. 9 is ablock diagram showing a configuration example of the NR gNB 2 accordingto the above embodiments. The configuration of the LTE eNB 1 may besimilar to that shown in FIG. 11. Referring to FIG. 11, the NR gNB 2includes a Radio Frequency transceiver 1101, a network interface 1103, aprocessor 1104, and a memory 1105. The RF transceiver 1101 performsanalog RF signal processing to communicate with NG UEs including the UE3. The RF transceiver 1101 may include multiple transceivers. The RFtransceiver 1101 is coupled to an antenna array 1102 and the processor1104. The RF transceiver 1101 receives modulated symbol data from theprocessor 1104, generates a transmission RF signal, and supplies thetransmission RF signal to the antenna array 1102. Further, the RFtransceiver 1101 generates a baseband reception signal based on areception RF signal received by the antenna array 1102 and supplies thebaseband reception signal to the processor 1104. The RF transceiver 1101may include an analog beamformer circuit for beam forming. The analogbeamformer circuit includes, for example, multiple phase shifters andmultiple power amplifiers.

The network interface 1103 is used to communicate with network nodes(e.g., the LTE eNB 1, the MME 5, and the S-GW 6). The network interface1103 may include, for example, a network interface card (NIC) conformingto the IEEE 802.3 series.

The processor 1104 performs digital baseband signal processing (i.e.,data-plane processing) and control-plane processing for radiocommunication. The processor 1104 may include multiple processors. Theprocessor 1104 may include, for example, a modem processor (e.g., aDigital Signal Processor (DSP)) that performs digital baseband signalprocessing and a protocol stack processor (e.g., a Central ProcessingUnit (CPU) or a Micro Processing Unit (MPU)) that performs thecontrol-plane processing. The processor 1104 may include a digitalbeamformer module for beam forming. The digital beamformer module mayinclude a Multiple Input Multiple Output (MIMO) encoder and a pre-coder.

The memory 1105 is composed of a combination of a volatile memory and anon-volatile memory. The volatile memory is, for example, a StaticRandom Access Memory (SRAM), a Dynamic RAM (DRAM), or a combinationthereof. The non-volatile memory is, for example, a mask Read OnlyMemory (MROM), an Electrically Erasable Programmable ROM (EEPROM), aflash memory, a hard disc drive, or any combination thereof. The memory1105 may include a storage located apart from the processor 1104. Inthis case, the processor 1104 may access the memory 1105 via the networkinterface 1103 or an I/O interface (not shown).

The memory 1105 may store one or more software modules (computerprograms) 1106 including instructions and data to perform processing bythe gNB 2 described in the above embodiments. In some implementations,the processor 1104 may be configured to load the software modules 1106from the memory 1105 and execute the loaded software modules, therebyperforming processing of the gNB 2 described in the above embodiments.

FIG. 12 is a block diagram showing a configuration example of the UE 3.A Radio Frequency (RF) transceiver 1201 performs analog RF signalprocessing to communicate with the eNB 1 and the gNB 2. The RFtransceiver 1201 may include multiple transceivers. The analog RF signalprocessing performed by the RF transceiver 1201 includes frequencyup-conversion, frequency down-conversion, and amplification. The RFtransceiver 1201 is coupled to an antenna array 1202 and a basebandprocessor 1203. The RF transceiver 1201 receives modulated symbol data(or OFDM symbol data) from the baseband processor 1203, generates atransmission RF signal, and supplies the transmission RF signal to theantenna array 1202. Further, the RF transceiver 1201 generates abaseband reception signal based on a reception RF signal received by theantenna array 1202 and supplies the baseband reception signal to thebaseband processor 1203. The RF transceiver 1201 may include an analogbeamformer circuit for beam forming. The analog beamformer circuitincludes, for example, multiple phase shifters and multiple poweramplifiers.

The baseband processor 1203 performs digital baseband signal processing(i.e., data-plane processing) and control-plane processing for radiocommunication. The digital baseband signal processing includes (a) datacompression/decompression, (b) data segmentation/concatenation, (c)composition/decomposition of a transmission format (i.e., transmissionframe), (d) channel coding/decoding, (e) modulation (i.e., symbolmapping)/demodulation, and (f) generation of OFDM symbol data (i.e.,baseband OFDM signal) by Inverse Fast Fourier Transform (IFFT).Meanwhile, the control-plane processing includes communicationmanagement of layer 1 (e.g., transmission power control), layer 2 (e.g.,radio resource management and hybrid automatic repeat request (HARQ)processing), and layer 3 (e.g., signaling regarding attach, mobility,and call management).

The digital baseband signal processing by the baseband processor 1203may include, for example, signal processing of a Packet Data ConvergenceProtocol (PDCP) layer, a Radio Link Control (RLC) layer, a MAC layer,and a PHY layer. Further, the control-plane processing performed by thebaseband processor 1203 may include processing of a Non-Access Stratum(NAS) protocol, an RRC protocol, and MAC CEs.

The baseband processor 1203 may perform MIMO encoding and pre-coding forbeam forming.

The baseband processor 1203 may include a modem processor (e.g., DSP)that performs the digital baseband signal processing and a protocolstack processor (e.g., a CPU or an MPU) that performs the control-planeprocessing. In this case, the protocol stack processor, which performsthe control-plane processing, may be integrated with an applicationprocessor 1204 described in the following.

The application processor 1204 is also referred to as a CPU, an MPU, amicroprocessor, or a processor core. The application processor 1204 mayinclude multiple processors (processor cores). The application processor1204 loads a system software program (Operating System (OS)) and variousapplication programs (e.g., a call application, a WEB browser, a mailer,a camera operation application, and a music player application) from amemory 1206 or from another memory (not shown) and executes theseprograms, thereby providing various functions of the UE 3.

In some implementations, as represented by a dashed line (1205) in FIG.12, the baseband processor 1203 and the application processor 1204 maybe integrated on a single chip. In other words, the baseband processor1203 and the application processor 1204 may be implemented in a singleSystem on Chip (SoC) device 1205. An SoC device may be referred to as asystem Large Scale Integration (LSI) or a chipset.

The memory 1206 is a volatile memory, a non-volatile memory, or acombination thereof. The memory 1206 may include multiple memory devicesthat are physically independent from each other. The volatile memory is,for example, an SRAM, a DRAM, or a combination thereof. The non-volatilememory is, for example, an MROM, an EEPROM, a flash memory, a hard discdrive, or any combination thereof. The memory 1206 may include, forexample, an external memory device that can be accessed from thebaseband processor 1203, the application processor 1204, and the SoC1205. The memory 1206 may include an internal memory device that isintegrated in the baseband processor 1203, the application processor1204, or the SoC 1205. Further, the memory 1206 may include a memory ina Universal Integrated Circuit Card (UICC).

The memory 1206 may store one or more software modules (computerprograms) 1207 including instructions and data to perform the processingby the UE 3 described in the above embodiments. In some implementations,the baseband processor 1203 or the application processor 1204 may loadthese software modules 1207 from the memory 1206 and execute the loadedsoftware modules, thereby performing the processing of the UE 3described in the above embodiments with reference to the drawings.

As described above with reference to FIGS. 11 and 12, each of theprocessors included in the eNB 1, the gNB 2, and the UE 3 according tothe above-described embodiments executes one or more programs includinginstructions to cause a computer to perform an algorithm described withreference to the drawings. The program(s) can be stored and provided toa computer using any type of non-transitory computer readable media.Non-transitory computer readable media include any type of tangiblestorage media. Examples of non-transitory computer readable mediainclude magnetic storage media (such as flexible disks, magnetic tapes,hard disk drives, etc.), optical magnetic storage media (e.g.,magneto-optical disks), Compact Disc Read Only Memory (CD-ROM), CD-R,CD-R/W, and semiconductor memories (such as mask ROM, Programmable ROM(PROM), Erasable PROM (EPROM), flash ROM, Random Access Memory (RAM),etc.). The program(s) may be provided to a computer using any type oftransitory computer readable media. Examples of transitory computerreadable media include electric signals, optical signals, andelectromagnetic waves. Transitory computer readable media can providethe program to a computer via a wired communication line (e.g., electricwires, and optical fibers) or a wireless communication line.

Other Embodiments

The above-described embodiments describe examples in which the SgNBAddition procedure following the SeNB Addition procedure is used. In theabove-described embodiments, an SgNB Modification procedure whichfollows the SeNB Modification procedure may instead be used in place ofthe SgNB Addition procedure. The MeNB 1 may send, for example, an SgNBModification Request message to the SgNB 2 in place of the SgNB AdditionRequest message (e.g., Step 501 shown in FIG. 5).

The MeNB 1 may perform UE Capability Coordination between the MeNB 1 andthe SgNB 2 before sending the radio bearer setup request (e.g., the SgNBAddition Request message or the SgNB Modification Request message) tothe SgNB 2. The MeNB 1 may send, for example, a UE CapabilityCoordination Request message to the SgNB 2, and receive a UE CapabilityCoordination Response message from the SgNB 2. In this Coordination, theMeNB 1 and the SgNB 2 may share (or negotiate) only a fixed UEcapabilities (e.g., capabilities that are not substantially changedwhile data is being transmitted or received in DC, or hard-splitcapabilities), such as RF capability (e.g., Band combination,measurement capability). The MeNB 1 and the SgNB 2 may also negotiatestatic UE capabilities (e.g., capabilities that are not dynamicallychanged during DC, or dynamically-shared capabilities), such ascapabilities related to the UE category specification (e.g., softbuffer/soft channel bit). Alternatively, the MeNB) 1 and the SgNB 2 mayshare static UE capabilities in the step of exchanging SeNB AdditionRequest/Acknowledge messages (or SeNB Modification Request/Acknowledgemessages).

The Information Elements included in the messages described in theabove-described embodiments (e.g., the SgNB Addition Request message,the SgNB Addition Request Acknowledge message, the RRC ConnectionReconfiguration message, the RRC Connection Reconfiguration Completemessage, the SgNB Reconfiguration Complete message, the Xn Setup Requestmessage, the Xn Setup Response message, the NR Handover Request message,the NR Handover Request Acknowledge message) are not limited to theabove-described ones. The Information Elements contained in theabove-described messages may be, for example, communicated andnegotiated in directions or between nodes different from those describedin the above embodiments for the purpose of performing DC between theLTE eNB 1 and the NR gNB 2, or performing a handover from E-UTRA to NR.As a more specific example, at least some of the information elementsincluded in the SgNB Addition Request message may be included in theSgNB Addition Request Acknowledge message. In addition or alternatively,at least a part of the information elements included in the SgNBAddition Request message may be included in an SLAP message sent fromthe EPC 4 (the MME 5) to the LTE eNB 1 (e.g., an S1AP: E-RAB SetupRequest message). It is possible to allow nodes related to DC performedbetween the LTE eNB 1 and the NR gNB 2 to share information needed forthe DC.

The operations and processes of the UE 2, the base stations (the LTE eNB1 and the NR gNB 2), and the core networks (the EPC 4 and the 5G-CN 7)described in the above embodiments may also be applied to Intra-NR DualConnectivity and an Inter-gNB Handover. It is possible, for example,that a configuration of the numerology may be different even betweenneighbour cells within a single NR system. Accordingly, when DualConnectivity or handover is executed, the numerology that should be usedin the secondary cell or the target cell may be configured per UE. To bemore specific, the secondary (or target) gNB may send to the UE 3, viathe primary (or source) gNB, an NR radio resource configurationexplicitly or implicitly indicating at least one dedicated numerologythat is included in multiple numerologies supported by one or more NRcells of the secondary (or target) gNB and is different from thereference numerology.

In the above embodiments, each numerology may be associated with one ormore network slices or network slice instances. The informationindicating the dedicated numerology(ies) described in the aboveembodiments may be, for example, information indicating a predeterminednetwork slice or network slice instance (e.g., network slice identity,network slice instance identity). Upon receiving the informationindicating the predetermined network slice or network slice instance,the UE 2 may detect the dedicated numerology that is associated withthis predetermined network slice or network slice instance. Further, thereference numerology may also be associated with a network slice ornetwork slice instance. In this case, the network slice or the networkslice instance associated with the reference numerology may be commonlyconfigured (or available) for UEs in a cell. In the case of E-UTRA-NRDual Connectivity in which E-UTRA and NR are connected to EPC, thenetwork slice may be a Dedicated Core network Node (DCN). In this case,a DCN identifier (e.g., DCN ID) may be associated with the dedicatednumerology.

The LTE eNB 1 and the NR gNB 2 described in the above embodiments may beimplemented based on a Cloud Radio Access Network (C-RAN) concept. TheC-RAN is also referred to as a Centralized RAN. In this case, processesand operations performed by each of the LTE eNB 1 and the gNB 2described in the above embodiments may be provided by a Digital Unit(DU) included in the C-RAN architecture, or by a combination of a DU anda Radio Unit (RU). The DU is also referred to as a Baseband Unit (BBU)or a Central Unit (CU). The RU is also referred to as a Remote RadioHead (RRH), a Remote Radio Equipment (RRE), a Distributed Unit (DU), ora Transmission and Reception Point (TRP). That is, processes andoperations performed by each of the LTE eNB 1 and the gNB 2 described inthe above embodiments may be provided by one or more radio stations (orRAN nodes).

Further, the above-described embodiments are merely examples ofapplications of the technical ideas obtained by the inventors. Thesetechnical ideas are not limited to the above-described embodiments andvarious modifications may be made thereto.

For example, the whole or part of the above embodiments can be describedas, but not limited to, the following supplementary notes.

(Supplementary Note 1)

A second radio access network (RAN) node to be used in a radiocommunication system that supports a first RAT and a second RAT, thesecond RAN node being associated with the second RAT, the second RANnode comprising:

a memory; and

at least one processor coupled to the memory and configured to send aradio resource configuration of the second RAT to a radio terminal via afirst RAN node associated with the first RAT, wherein

the radio resource configuration explicitly or implicitly indicates atleast one numerology that is included in multiple numerologies supportedby the second RAT and is different from a reference numerology.

(Supplementary Note 2)

The second RAN node according to Supplementary Note 1, wherein eachnumerology includes at least one of subcarrier spacing, systembandwidth, a Transmission Time Interval length, subframe duration, slotduration, the number of slots per subframe, a Cyclic prefix length,symbol duration, and the number of symbols per subframe.

(Supplementary Note 3)

The second RAN node according to Supplementary Note 1 or 2, wherein theat least one processor is configured to generate the radio resourceconfiguration for dual connectivity that uses the first RAT as a primaryRAT and the second RAT as a secondary RAT.

(Supplementary Note 4)

The second RAN node according to Supplementary Note 3, wherein the atleast one processor is configured to receive a radio bearer setuprequest from the first RAN node, select at least one numerologyaccording to requirements for a radio bearer of the second RAT indicatedby the radio bearer setup request, and include in the radio resourceconfiguration an information element explicitly or implicitly indicatingthe selected at least one numerology.

(Supplementary Note 5)

The second RAN node according to Supplementary Note 1 or 2, wherein theat least one processor is configured to generate the radio resourceconfiguration for an Inter-RAT handover of the radio terminal from thefirst RAT to the second RAT.

(Supplementary Note 6)

The second RAN node according to any one of Supplementary Notes 1 to 5,wherein the reference numerology defines a reference subframeconfiguration for a carrier that the second RAT supports.

(Supplementary Note 7)

The second RAN node according to any one of Supplementary Notes 1 to 6,wherein the at least one processor is configured to notify the first RANnode of the reference numerology in a setup procedure of an inter-basestation interface between the first RAN node and the second RAN node.

(Supplementary Note 8)

The second RAN node according to Supplementary Note 6, wherein the atleast one processor is configured to send to the radio terminal, via thefirst RAN node, a configuration for measurement on the carrier accordingto the reference numerology.

(Supplementary Note 9)

A first radio access network (RAN) node to be used in a radiocommunication system that supports a first RAT and a second RAT, thefirst RAN node being associated with the first RAT, the first RAN nodecomprising:

a memory; and

at least one processor coupled to the memory and configured to receive aradio resource configuration of the second RAT from a second RAN nodeassociated with the second RAT and send the radio resource configurationto a radio terminal, wherein

the radio resource configuration explicitly or implicitly indicates atleast one numerology that is included in multiple numerologies supportedby the second RAT and is different from a reference numerology.

(Supplementary Note 10)

The first RAN node according to Supplementary Note 9, wherein eachnumerology includes at least one of subcarrier spacing, systembandwidth, a Transmission Time Interval length, subframe duration, slotduration, the number of slots per subframe, a Cyclic prefix length,symbol duration, and the number of symbols per subframe.

(Supplementary Note 11)

The first RAN node according to Supplementary Note 9 or 10, wherein theat least one processor is configured to receive the radio resourceconfiguration from the second RAN node for dual connectivity that usesthe first RAT as a primary RAT and the second RAT as a secondary RAT.

(Supplementary Note 12)

The first RAN node according to Supplementary Note 9 or 10, wherein theat least one processor is configured to receive the radio resourceconfiguration from the second RAN node for an Inter-RAT handover of theradio terminal from the first RAT to the second RAT.

(Supplementary Note 13)

The first RAN node according to any one of Supplementary Notes 9 to 12,wherein the reference numerology defines a reference subframeconfiguration for a carrier that the second RAT supports.

(Supplementary Note 14)

The first RAN node according to Supplementary Note 13, wherein the atleast one processor is configured to send, to the radio terminal, aconfiguration for measurement on the carrier according to the referencenumerology.

(Supplementary Note 15)

The first RAN node according to any one of Supplementary Notes 9 to 13,wherein the at least one processor is configured to receive thereference numerology from the second RAN node in a setup procedure of aninter-base station interface between the first RAN node and the secondRAN node.

(Supplementary Note 16)

A radio terminal to be used in a radio communication system thatsupports a first RAT and a second RAT, the radio terminal comprising:

at least one wireless transceiver configured to communicate with a firstradio access network (RAN) node associated with the first RAT andcommunicate with a second RAN node associated with the second RAT; and

at least one processor configured to receive a radio resourceconfiguration of the second RAT from the second RAN node via the firstRAN node, wherein

the radio resource configuration explicitly or implicitly indicates atleast one numerology that is included in multiple numerologies supportedby the second RAT and is different from a reference numerology.

(Supplementary Note 17)

The radio terminal according to Supplementary Note 16, wherein eachnumerology includes at least one of subcarrier spacing, systembandwidth, a Transmission Time Interval length, subframe duration, slotduration, the number of slots per subframe, a Cyclic prefix length,symbol duration, and the number of symbols per subframe.

(Supplementary Note 18)

The radio terminal according to Supplementary Note 16 or 17, wherein theat least one processor is configured to receive the radio resourceconfiguration for dual connectivity that uses the first RAT as a primaryRAT and the second RAT as a secondary RAT.

(Supplementary Note 19)

The radio terminal according to Supplementary Note 16 or 17, wherein theat least one processor is configured to receive the radio resourceconfiguration for an Inter-RAT handover of the radio terminal from thefirst RAT to the second RAT.

(Supplementary Note 20)

The radio terminal according to any one of Supplementary Notes 16 to 19,wherein the reference numerology defines a reference subframeconfiguration for a carrier that the second RAT supports.

(Supplementary Note 21)

A method for a second radio access network (RAN) node used in a radiocommunication system that supports a first RAT and a second RAT, thesecond RAN node being associated with the second RAT, the methodcomprising:

sending a radio resource configuration of the second RAT to a radioterminal via a first RAN node associated with the first RAT, wherein

the radio resource configuration explicitly or implicitly indicates atleast one numerology that is included in multiple numerologies supportedby the second RAT and is different from a reference numerology.

(Supplementary Note 22)

A method for a first radio access network (RAN) node used in a radiocommunication system that supports a first RAT and a second RAT, thefirst RAN node being associated with the first RAT, the methodcomprising:

receiving a radio resource configuration of the second RAT from a secondRAN node associated with the second RAT; and

sending the radio resource configuration to a radio terminal, wherein

the radio resource configuration explicitly or implicitly indicates atleast one numerology that is included in multiple numerologies supportedby the second RAT and is different from a reference numerology.

(Supplementary Note 23)

A method for a radio terminal used in a radio communication system thatsupports a first RAT and a second RAT, the method comprising:

receiving a radio resource configuration of the second RAT from a secondradio access network (RAN) node associated with the second RAT via afirst RAN node associated with the first RAT, wherein

the radio resource configuration explicitly or implicitly indicates atleast one numerology that is included in multiple numerologies supportedby the second RAT and is different from a reference numerology.

(Supplementary Note 24)

A program for causing a computer to perform a method for a second radioaccess network (RAN) node used in a radio communication system thatsupports a first RAT and a second RAT, the second RAN node beingassociated with the second RAT, wherein the method comprises:

sending a radio resource configuration of the second RAT to a radioterminal via a first RAN node associated with the first RAT, wherein

the radio resource configuration explicitly or implicitly indicates atleast one numerology that is included in multiple numerologies supportedby the second RAT and is different from a reference numerology.

(Supplementary Note 25)

A program for causing a computer to perform a method for a first radioaccess network (RAN) node used in a radio communication system thatsupports a first RAT and a second RAT, the first RAN node beingassociated with the first RAT, wherein the method comprises:

receiving a radio resource configuration of the second RAT from a secondRAN node associated with the second RAT; and

sending the radio resource configuration to a radio terminal, wherein

the radio resource configuration explicitly or implicitly indicates atleast one numerology that is included in multiple numerologies supportedby the second RAT and is different from a reference numerology.

(Supplementary Note 26)

A program for causing a computer to perform a method for a radioterminal used in a radio communication system that supports a first RATand a second RAT, wherein the method comprises:

receiving a radio resource configuration of the second RAT from a secondradio access network (RAN) node associated with the second RAT via afirst RAN node associated with the first RAT, wherein

the radio resource configuration explicitly or implicitly indicates atleast one numerology that is included in multiple numerologies supportedby the second RAT and is different from a reference numerology.

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2017-000798, filed on Jan. 5, 2017, thedisclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

-   1 eNodeB (eNB)-   2 gNodeB (gNB)-   3 User Equipment (UE)-   4 Evolved Packet Core (EPC)-   5 Mobility Management Entity (MME)-   7 5G Core Network (5G-CN)-   1101 RF Transceiver-   1104 Processor-   1105 Memory-   1201 RF Transceiver-   1203 Baseband Processor-   1204 Application Processor-   1206 Memory

The invention claimed is:
 1. A second radio access network (RAN) node tobe used in a radio communication system configured to support a firstradio access technology (RAT) and a second RAT, the second RAN nodebeing associated with the second RAT, the second RAN node comprising: amemory storing instructions; and at least one processor configured toprocess the instructions to: receive a radio bearer setup request from afirst RAN node associated with the first RAT; include in a radioresource configuration of the second RAT an information elementindicating at least one numerology according to requirements for a radiobearer of the second RAT indicated by the radio bearer setup request;and transmit the radio resource configuration to a radio terminal viathe first RAN node, wherein the at least one numerology is included inmultiple numerologies supported by the second RAT and is different froma reference numerology, and the reference numerology defines a referencesubframe configuration for a carrier that the second RAT supports. 2.The second RAN node according to claim 1, wherein each numerologyincludes at least one of subcarrier spacing, system bandwidth, aTransmission Time Interval length, subframe duration, slot duration, thenumber of slots per subframe, a Cyclic prefix length, symbol duration,and the number of symbols per subframe.
 3. The second RAN node accordingto claim 1, wherein the at least one processor is configured to processthe instructions to generate the radio resource configuration for dualconnectivity that uses the first RAT as a primary RAT and the second RATas a secondary RAT.
 4. The second RAN node according to claim 1, whereinthe at least one processor is configured to process the instructions totransmit, to the radio terminal via the first RAN node, a measurementconfiguration of at least one cell provided by the second RAN node onthe carrier according to the reference numerology.
 5. The second RANnode according to claim 1, wherein the at least one processor isconfigured to process the instructions to select the at least onenumerology according to the requirements for the radio bearer of thesecond RAT indicated by the radio bearer setup request.
 6. The secondRAN node according to claim 1, wherein the reference numerology is usedfor at least detection of a synchronisation signal.
 7. A first radioaccess network (RAN) node to be used in a radio communication systemconfigured to support a first radio access technology (RAT) and a secondRAT, the first RAN node being associated with the first RAT, the firstRAN node comprising: a memory storing instructions; and at least oneprocessor configured to process the instructions to: transmit a radiobearer setup request indicating at least requirements for a radio bearerof the second RAT, to a second RAN node associated with the second RAT;receive a radio resource configuration of the second RAT, from thesecond RAN node; and transmit the radio resource configuration to aradio terminal, wherein the radio resource configuration indicates atleast one numerology that is included in multiple numerologies supportedby the second RAT, is according to the requirements, and is differentfrom a reference numerology, and the reference numerology defines areference subframe configuration for a carrier that the second RATsupports.
 8. The first RAN node according to claim 7, wherein eachnumerology includes at least one of subcarrier spacing, systembandwidth, a Transmission Time Interval length, subframe duration, slotduration, the number of slots per subframe, a Cyclic prefix length,symbol duration, and the number of symbols per subframe.
 9. The firstRAN node according to claim 7, wherein the at least one processor isconfigured to process the instructions to receive, from the second RANnode, the radio resource configuration for dual connectivity that usesthe first RAT as a primary RAT and the second RAT as a secondary RAT.10. The first RAN node according to claim 7, wherein the at least oneprocessor is configured to process the instructions to transmit ameasurement configuration of at least one cell provided by the secondRAN node on the carrier according to the reference numerology.
 11. Thefirst RAN node according to claim 7, wherein the reference numerology isused for at least detection of a synchronisation signal.
 12. A radioterminal to be used in a radio communication system configured tosupport a first radio access technology (RAT) and a second RAT, theradio terminal comprising: a memory storing instructions; and at leastone processor configured to process the instructions to: communicatewith a first radio access network (RAN) node associated with the firstRAT and a second RAN node associated with the second RAT; and receive aradio resource configuration of the second RAT from the second RAN nodevia the first RAN node, wherein the radio resource configurationindicates at least one numerology that is included in multiplenumerologies supported by the second RAT, is according to requirementsfor a radio bearer which is established on the second RAT, and isdifferent from a reference numerology, the reference numerology definesa reference subframe configuration for a carrier that the second RATsupports, and the at least one processor is further configured toprocess the instructions to receive from the second RAN node, via thefirst RAN node, a measurement configuration of at least one cellprovided by the second RAN node on the carrier according to thereference numerology.
 13. The radio terminal according to claim 12,wherein each numerology includes at least one of subcarrier spacing,system bandwidth, a Transmission Time Interval length, subframeduration, slot duration, the number of slots per subframe, a Cyclicprefix length, symbol duration, and the number of symbols per subframe.14. The radio terminal according to claim 12, wherein the at least oneprocessor is configured to process the instructions to receive the radioresource configuration for dual connectivity that uses the first RAT asa primary RAT and the second RAT as a secondary RAT.
 15. A method for asecond radio access network (RAN) node to be used in a radiocommunication system configured to support a first radio accesstechnology (RAT) and a second RAT, the second RAN node being associatedwith the second RAT, the method comprising: receiving a radio bearersetup request from a first RAN node associated with the first RAT;including in a radio resource configuration of the second RAT aninformation element indicating at least one numerology according torequirements for a radio bearer of the second RAT indicated by the radiobearer setup request; and transmitting the radio resource configurationto a radio terminal via the first RAN node, wherein the at least onenumerology is included in multiple numerologies supported by the secondRAT and is different from a reference numerology, and the referencenumerology defines a reference subframe configuration for a carrier thatthe second RAT supports.
 16. A method for a first radio access network(RAN) node to be used in a radio communication system configured tosupport a first radio access technology (RAT) and a second RAT, thefirst RAN node being associated with the first RAT, the methodcomprising: transmitting a radio bearer setup request indicating atleast requirements for a radio bearer of the second RAT, to a second RANnode associated with the second RAT; receiving a radio resourceconfiguration of the second RAT, from the second RAN node; andtransmitting the radio resource configuration to a radio terminal,wherein the radio resource configuration indicates at least onenumerology that is included in multiple numerologies supported by thesecond RAT, is according to the requirements, and is different from areference numerology, and the reference numerology defines a referencesubframe configuration for a carrier that the second RAT supports.
 17. Amethod for a radio terminal to be used in a radio communication systemconfigured to support a first radio access technology (RAT) and a secondRAT, the method comprising: communicating with a first radio accessnetwork (RAN) node associated with the first RAT and a second RAN nodeassociated with the second RAT; and receiving a radio resourceconfiguration of the second RAT from the second RAN node via the firstRAN node, wherein the radio resource configuration indicates at leastone numerology that is included in multiple numerologies supported bythe second RAT, is according to requirements for a radio bearer which isestablished on the second RAT, and is different from a referencenumerology, the reference numerology defines a reference subframeconfiguration for a carrier that the second RAT supports, and the methodfurther comprises receiving from the second RAN node, via the first RANnode, a measurement configuration of at least one cell provided by thesecond RAN node on the carrier according to the reference numerology.